1. Field of the Invention
The present invention relates to a device for delivering medicative liquids to the eye. In particular, the present invention relates to a porous, flexible ocular appliance for delivering short-duration topical anesthetic agents and other medication to the eye.
2. Discussion of Background
Topical anesthetics, antibiotics and other medications are usually delivered to the eye by placing liquids or salves directly into the eye with a squeeze tube, eye dropper, or as an eye wash. The person administering the medication may place a finger over the tear duct to help keep the medication in the eye and prevent it from entering the patient's system and being carried throughout the body. Once placed in the eye, the liquid is dispersed over the eyeball by the lacrimal fluids (tears).
Liquids can also be delivered using contact lenses and other types of ocular inserts or appliances. So-called "soft" contact lenses made of highly porous plastic can absorb half or more of their volume in water or other fluids. This type of lens can be soaked in a liquid medication and then inserted into the eye to deliver the medication. Other types of ocular inserts designed for long-term dispensing of medication include a frustospherical, annular ring made of a semipermeable polymeric material, shaped to conform to the curvature of the eye (Rosenwald, U.S. Pat. No. 4,484,922). The device is placed on the cornea, and extends over the eyeball and into the conjunctival sacs behind the upper and lower eyelids. Hughes, et al. (U.S. Pat. No. 4,201,210) and Higuchi, et al. (U.S. Pat. No. 3,995,635) describe flexible tubular devices sized for insertion into the conjunctival sac of the eye. Both devices can be made of bioerodable materials, or inert tubing with holes for distributing the medication.
The corneal region of the eye is highly sensitive to the presence of foreign bodies, which can be a source of discomfort, irritation and even injury to the patient. The sensation of a foreign body in the eye--including an insert designed for the delivery of medication--stimulates natural defense mechanisms which protect the eye against injury. For example, the lacrimal glands become more active, producing tears that dilute liquids and wash solid objects from the eye; the eyeball tends to rotate up and down while the eyelids blink in order to expel the object. When liquid medication is administered with an eye dropper or the like, the liquid may not be distributed uniformly over the eyeball, and a significant portion may spill out of the eye. This is a particular problem in the case of topical anesthetic agents used for ophthalmic surgery, since it is important to provide the correct dose of the selected anesthetic and also to distribute it uniformly over the eye.
Many types of ocular inserts are designed for long-term delivery of medication, and thus, are not suited for the relatively rapid (no more than a few minutes) delivery time needed for topical anesthetics. Furthermore, many inserts are bulky and uncomfortable, or must be shaped to fit the eye. Consequently, there is a need for an insert designed for the rapid delivery of liquid medication to the eye. The insert should be capable of delivering the medication uniformly, be comfortable for the patient, easy to use, usable on all or most patients without the need for individual fitting, and simple and economical to manufacture.